Method of treating lubricating oils



Patented May 31, 1938 UNITED STATES A'E'ENT OFFICE Jere C. Showalter, Goose Creek, Tex., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application November 28, 1936, Serial No. 113,252

7 Claims.

This invention relates to the treating of lubricating oils and is more particularly concerned with the prevention of wax haze.

In the refining of lubricating oils it is customary to subject the oil, whether a distillate or a residual, to treatment with sulfuric acid and thereafter to remove the sludge formed in this treatment. It has been found that many of these oils, even those which contain relatively small amounts of wax, develop a wax haze after a sulfuric acid treat, whereas no such haze may have appeared prior to the acid treat. It is concluded from this observation that the acid treat causes the removal in the sludge of certain natural haze inhibitors which may be present in the oil.

The formation of wax haze after acid treating is highly objectionable. It may be partially overcome by dewaxing, but in the case of oils containing only small amounts of wax, a special dewaxing step merely to remove haze is unduly expensive and may not even then entirely overcome the difficulty.

It is an object of the present invention to avoid the formation of wax haze in acid treated oils. The invention is particularly concerned with, although not limited to, oils which naturally contain only small amounts of wax such as lubricating fractions derived from Coastal or Colombian crudes.

According to the present invention a small quantity of an acid sludge obtained in the acid treating of a paraffin base oil is added to the raw lubricating oil to be treated. The quantity of acid sludge added to the raw stock may vary from .1 to about 3%, although with amounts as large as 3% more acid may be required in the subsequent treating to obtain the proper color.

The acid sludge used as the addition agent to the raw lubricating stock is preferably obtained from a residual stock derived from crudes such as Salt Flat, Panhandle, Deep Sand Reagan, etc. which are essentially parafiin base. The sludge is formed in the usual manner byadding sulfuric acid to the residual oil accompanied by vigorous agitation, and thereafter allowing the mixture to settle. The sludge layer is then removed and is available for use according to the present invention.

It is not definitely known why the addition of small quantities of acid sludge from a parafiinbase oil to an oil derived from a non-paraflin base crude will prevent the formation of a wax haze on acid treating the latter. It is believed, however, that a natural haze inhibitor is present in the acid sludge and that when a small quantity is added to a raw lubricating stock this small quantity is not precipitated during subsequent acid treating, so that the natural inhibitor remains in the oil. 5

The acid sludge may be added to the raw lubricating oil either prior to or after acid and clay treating of the latter. It is preferable, however, to add it prior to any refining treatment.

In many cases it is desirable to make a blend of the acid sludge with a small quantity of the raw lubricating oil and then to add this blend in varying amounts to the remainder of the raw stock. In this way just enough of the sludge can be added to accomplish haze prevention with- 15 out adversely affecting the color of the oil.

The following examples illustrate the invention:

Example 1 1% of an acid sludge from a Deep Sand Reagan residuum is added to a batch of a Coastal Distillate containing about 1% wax. This mixture is then treated with 25 lbs. of 98% sulfuric acid per barrel, and thereafter is contacted in the acid state with 0.75 lb. of clay per gallon. 25

Example 2 Another batch of the same Coastal Distillate is treated in exactly the same manner as in Example 1 except that no acid sludge is added. 30

The two treated oils are placed in storage at a temperature of 48 F; for observation. At the end of 24 hours the oil to which no acid sludge had been added shows a heavy flocculent wax formation throughout the mass. The oil to which 30 the acid sludge had been added is still bright at the end of 1224 hours.

This invention is not limited to any theories of the mechanism of haze formation nor to any details which have been given merely for purposes of illustration, but is limited only in and by the following claims in which it is intended to claim all novelty inherent in the invention.

I claim:

1. Method of preventing the formation of a wax haze in acid treated lubricating oils derived from petroleum naturally containing only small amounts of wax which comprises adding to the raw lubricating oil prior to acid treating a small quantity of an acid sludge obtained in the acid 50 treating of a lubricating oil derived from a paraflin base petroleum.

2. Method according to claim 1 in which the quantity of acid sludge added to the raw lubricating oil varies from .1 to about 3%. 55

3. Method according to claim 1 in which the acid sludge added to the raw lubricating oil is derived from the acid treating of a lubricating oil derived from a crude of the type of Salt Flat, Panhandle and Deep Sand Reagan. v

4. Method according to claim 1 in which the acid sludge added to the raw lubricating oil is obtained from the acid treating of a residual lubricating fraction of a parafiin base crude.

5. Method for preventing the formation of a wax haze in acid treated lubricating oils derived from non-parafiin base crude petroleum which comprises adding tothe raw lubricating stock prior to acid treating from .1 to 3% of an acid sludge obtained in the acid treating of a residual lubricating fraction derived from a paraflin base crude.

which comprises'preparing a blend of an acid sludge obtained in the acid treating of a lubricating oil derived from a paraffin base crude and a portion of the raw lubricating stock to be treated and then adding an efiective quantity of this blend to the remainder of the raw lubricating stock.

J ERE C. SHOWALTERI. 

